Lecture 15

Name the two principle pathways:

The typical chain of neurons involves
First order neuron: The cell body of the afferent neuron in the ____ ____ ____:
Second order neuron: found in the ____ horn of the spinal cord or the _____ ____.
Third order neuron: found in the _____.

Describe the three main levels of neural integration:

_____ level– Information aboutinternal and externalenvironment _____ level– Ascending pathwaysto the brain
_____ level– Allows us to beaware of stimuli anddiscriminate abouttheir characteristics

Organization of Somatosensory System
____ ____– Cell body of theafferent neuron in the dorsal root ganglion
____ ____– Neuron in the dorsal horn of spinal cord or medulla oblongata
_____ _____– Neuron in the thalamus

_____ _____ _____ neurons: respond to fine touch and pressure and pressure; joint, tendon, and muscle change; and pain and temperature.

____ _____ nuclei: relay fine touch and sensations.

_____ _____: contains axons that carry sensory info to the ventrolateral thalamus.

_____ _____: relays sensory information to the somatosensory cortex.

_____ _____ tract: receives input from pain and temperature neurons and then joinst hte pathway called the ______ leminiscus.

Regarding the Dorsal Column
_____ afferents ascend all the way to the medulla.
- (ipsilaterally or contralaterally)
- found in the (ventral or dorsal) portion of the cord
- pass through the ____ fasciculus (leg) and then through the ____ fasciculus (arm).

Regarding the Dorsal Column
_____ afferents cross at the medulla.
- (ascend or descend) at the medial leminiscus
- synapse at the ______
- ascend to the ______

Regarding the Spinothalamic Tract
____ afferents enter spinal cord _____ and pass throught the dorsal horn laminae.
- laminae I, V- ___ fibers
- laminae II- ___ fibers
____ afferents cross over via the _____ _____.
_____ afferents ascend via the _____ tract. and synapse at the _____. Final afferents _____ to the cortex.

______ tract: projects info about painful stimuli to VPL (called the neospinothalamic tract) also projects info to intralaminar nuclei (important for emotion component of pain).

______ tract: transmits sensory info to neurons in reticual formation which then project to intraluminar nuclei (part of paleospinothalamic tract)

_______ tract: terminates in midbrain, tectum, and periaqeuductal gray, integrates somatic sensation with visual and auditory info.

The ___ ____ fascicle transmits info from leg and lower trunk.
The ___ ____ fascicle transmits info from the upper trunk and head.
The two halves of the spinal cord are separated by dorsal ___ ____.
The cuneate and gracile fascicles are separated by the dorsal ____ ____.

The organization of the dorsal columns is called _____.

Ascending axons of the spinothalamic system originate in the spinal (gray or white) matter.
Decussation occurs at the (dorsal or ventral) commissure.

____ ____ ____ neurons carry fine touch and pressure info.
Have (large, small) (myelinated, unmyelinated) axons whose receptors are located in the skin, muscles, and tendons.
Fine touch and pressure axons, ascend (ipsilaterally, contralaterally) forming the spinothalamic tract to the neocortex.

Primary somatic sensory cortex has cytoarchitectonic divisions _, _, __, __.
Info from deep structures = __, and _ (course representation).
Info from mechanoreceptors of skin= __ and _.
Limb position= __ and _.
Touch perception= __ an _.

The primary somatic sensory cortex is located in the ____ ____.
Axons travel from ___ to cortex through (anterior or posterior) limb of ____ ____.

______: final stage of sensory processing. Allows us to be aware of stimuli and discriminate about their characteristics.

As sensory info reaches the ____, they are perceived in a crude sense.

The thalamus projects fibers to the ____ _____ cortex.

Because fine touch and pressure sensations are conducted to the brain ipsilaterally though the dorsal column/medial lemniscus system, they are lost (above or below) the level of damage (contralateral or ipsilateral).

Because pain and temperature sensations are conducted to the thalamus contralaterally through the thalamus contralaterally thourgh the ventral spinaothalamic tract, they are lost (above or below) the level of damage (ipsilaterally or contralaterlly)

Where would sensation be lost if Left gracile fasciculus were damaged.

What would be lost if left dorsal column (both gracile and cuneate fasciculi) were damaged?

What would be lost if right medial lemniscus in the medulla were damaged?

Three key sensory deficits that follow spinal cord injury permit localization of trauma. Describe.

_____ _____ Syndrome: damage to one half of spinal cord. Deficits in touch and limb position sense are ipsilateral. Deficits in pain and temperature are contralateral. Injury is at level of most rostral dermatorme where tactile sensation is impaired and few segments higher than the most rostral dermatome where pain is impaired.

_____ ____: advanced syphilis, large diameter axons last, damage of DCML lemniscal system.

_______: a cavity forms in the central portion of the spinal cord, destroys axons of AL decussating at ventral commisure, only affects level of lesion, everything below is OK.